Mechanical impact printers are known to the prior art for imprinting a succession of characters, which may comprise machine-readable and human-readable alphanumeric characters, on an elongated strip of print stock. In such printers, the elongated strip is drawn under tension from a rotatable print stock supply reel by a rotating, print stock drive capstan and an associated pinch roller, and moved along a predetermined path through a print station where the characters are successively imprinted. The print station may include a continuously rotating cylindrical print wheel having located on a circumferential surface thereof a plurality of raised elements representing the characters to be imprinted, and a hammer mechanism including at least one hammer which has a selectively controllable, pivotal movement in a predetermined plane, whereby a face of the hammer during hammer travel impacts the elongated strip and an interposed ink ribbon against one of the elements on the print wheel, resulting in imprinting of a character.
In one application, the print stock has a thermally-sensitive adhesive layer formed on the print stock surface that faces the hammer mechanism, whereby the hammer face impacts the adhesive layer to drive the print stock and the interposed ink ribbon into contact with an element on the print wheel. After imprinting of a plurality of successive characters on the print stock and concurrent advancement of a predetermined length of the print stock through the print station, a cutter severs the predetermined length to accordingly form a label which may be removed from the printer. The printer is then caused to advance successive lengths of the print stock through the print station in order to form successive labels. In order to apply each label to a desired surface, the label is heated to activate the adhesive layer thereon.
The cutter includes a movable blade and a stationary blade, each having an elongated cutting edge formed thereon. Upon the application of an electrical signal to a solenoid mechanically coupled to the movable blade, the movable blade is moved from a rest position towards the stationary blade, whereby the cutting edges thereof contact each to sever the print stock to form a label. Upon removal of the electrical signal from the solenoid, a spring returns the movable blade to its rest position.
As the rate of production of labels by the printer is increased, the time required for the cutter to completely sever a label, and thus the speed of movement of the movable blade, must be increased. At relatively low label production rates, cutters of the type described provide acceptable operation and cleanly sever the print stock. However, at relatively high label production rates, the cutters of the prior art tend to provide ragged cuts, and in some instances may not completely sever the print stock. Accordingly, the label production rate of the printer is limited by the maximum speed at which the cutter can satisfactorily operate.
In the application discussed above in which the print stock is provided with an adhesive layer, it has also been found that the material of the adhesive layer tends to build up on the cutting edges of the movable and stationary blades, thereby resulting in increasingly ragged cuts which necessitate frequent cleaning of the cutting edges and a consequent lowering of the label production rate.
It is therefore an object of this invention to provide an improved label cutter for mechanical impact printers.
It is another object of this invention to provide such a label cutter which cleanly severs an elongated strip of print stock at very high operating speeds, thereby allowing a high rate of label production by the printer.
It is another object of this invention to provide such a label cutter which does not require frequent cleaning when used with print stock having an adhesive layer formed thereon.